I am using a CPAN module (Parse::RecDescent, as it happens) which prints output to stderr. My program, on the other hand, uses a logging module (based on log4perl) and I want to direct all output through my own logging module. I do not want to change the code of P::RD and it is not convenient to inherit P::RD, in order to change its behaviour. (NB When I say "prints output to stderr", I mean literally "print STDERR". If it was using warn(), I could simply install a __WARN__ handler.)

The obvious solution would appear to be to attach an output filter to my own program's STDERR. However, I find to my chagrin that I do not know how to do so :-( Attaching an output filter to my own program's STDOUT is straightforward. For example:

attach_stdout_filter;
while (<>) { print; }

sub attach_stdout_filter {
    my($pid);
    return if $pid = open(STDOUT, '|-');
    defined $pid or die "Cannot fork: $!\n";

    # child
    while (<STDIN>) { s/foo/bar/; print; }
}

[download]

Does anybody have a similar example which attaches an output filter to STDERR?

Cheers
Kevin

In reply to Filtering my own stderr by ruscoekm

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